The problem with jamming is that in order to be effective the transponder has to be very "loud", which means it can be destroyed by a missile which is built to

The problem with jamming is that in order to be effective the transponder has to be very "loud", which means it can be destroyed by a missile which is built to target the "loudest" object in front of it. Active radar can partially avoid these systems by turning off during inactivity, but jamming has to be continuous to really be effective